PhD

dissertationFragmentation processes of uridine-(TMS)(,4) were investigated using selectively deuterium and ('18)O labeled uridine. Decomposition pathways of uridine-(TMS)(,4) were measured by two metastable ion techniques, and plausible ion structures have been deduced from isotopic labeling data and mechanistic considerations. In addition, 128 silylated nucleoside mass spectra were examined to detect common characteristics for each class of nucleosides, for example, C-C versus C-N glycosidic bond, purine versus pyrimidine nucleosides, and (alpha) versus (beta) anomer. An Application of the knowledge of nucleoside fragmentation processes was shown by the structural characterization of a modified nucleoside isolated from Halococcus morrhuae tRNA. The utility of this knowledge for establishing the location of substituents and isotopic labels in the nucleoside skeleton was also described. The use of high resolution mass spectrometry to analyze and identify nucleoside components in tRNA hydrolysates was studied. The optimal experimental conditions: method of ionization, rate of heating the sample without defocusing the ion source, the resolution required to unequivocally determine the existence of a modified nucleoside in the hydrolysates, the sensitivity of this methodology, and the tradeoff between resolution and sensitivity were investigated and described. The procedures involved for the analysis of the high resolution mass spectrometric data were discussed in detail. Using E. coli tRNA('Phe) and tRNA('Glu) as models, modified nucleosides which occur only once in the tRNAs were identified with as little as 1 (mu)g of the tRNA hydrolysate. Resolution of 20,000 (10% valley definition) was found to be the best for the analysis of tRNA hydrolysate mixtures in terms of both resolution and sensitivity. The applications of this methodology were shown by the identification of N-{(9-(beta)-D-ribofuranosyl)-2-methylthiopurin-6yl-carbamoyl}threonine in tRNA(,1)('Lys) and tRNA(,3)('Lys) of B. subtilis. The procedure and application of this technique for the analysis of tRNAs of unknown components were also described with a tRNA('Leu) isolated from Morris hepatoma as an example

Syntheses of model oligosaccharides of biological significance. X. Syntheses and NMR and mass spectral analysis of trideuteriomethyl di-3,6-O-(4-O-\u3b2-D-galactopyranosyl-2-acetamido-2-deoxy-\u3b2-D-glucopyranosyl)-\u3b2-D-galactopyranoside: the I antigen branchpoint penta- and tetrasaccharides and a related trisaccharide

As part of our studies of complex oligosaccharides, in particular their three-dimensional structure, we have synthesized the antigen I branchpoint penta- and tetrasaccharides. The unbranched trisaccharide 3D was also synthesized, and its derivative 3B served as the intermediate for the synthesis of higher oligosaccharides. NMR spectra of major intermediates as well as of the final oligosaccharides were completely assigned. Mass spectra of the synthetic intermediates and the final oligosaccharides were analyzed and compared with those of a similar group of oligosaccharides containing L-fucose, N-acetyl-D-glucosamine, and D-galactose. Certain observations were made that could be utilized in the interpretation of mass spectra for the structural determination of protected oligosaccharides during the synthesis. Keywords: oligosaccharide synthesis, I antigen, carbohydrate mass spectrometry, carbohydrate NMR spectrometry, Gal-GlcNAc oligomers.Peer reviewed: YesNRC publication: N

Chemical structures of the core regions of campylobacter jejuni serotypes o:1, o:4, o:23, and o:36 lipopolysaccharides

Complete structures, including the location of N-acetylneuraminic acid (Neu5Ac) residues, were assigned for the core regions of Campylobacter jejuni serotypes 0:1, 0:4, and 0:23 and 0:36 lipopolysaccharides (LPS). In continuation of earlier studies, structure determinations of liberated oligosaccharides and, where necessary, of intact LPS, were by H-1-NMR spectroscopy, Smith degradation, chromium trioxide and enzymic degradations, in conjunction With methylation studies supported by fast-atom-bombardment mass spectrometry and linkage analyses by gas chromatography/mass spectrometry. It was concluded on the basis of the following structures, in which each was linked 1-->5 to a terminal 3-deoxy-D-manno-octulosonic acid residue, that the core regions with qualititatively similar sugar compositions showed serotypic differences in one or more of their sequences, linkage types, and anometic configurations: [GRAPHICS] The outer regions of each structure carry Neu5Ac residues linked 2-->3 to available beta-D-Galp residues and show striking similarities with various glycosphingolipids of the ganglioside family. However, Neu5Ac epitopes are not apparently involved in determining serospecificity

Chemical structures of the core regions of campylobacter jejuni serotypes o:1, o:4, o:23, and o:36 lipopolysaccharides

Complete structures, including the location of N-acetylneuraminic acid (Neu5Ac) residues, were assigned for the core regions of Campylobacter jejuni serotypes 0:1, 0:4, and 0:23 and 0:36 lipopolysaccharides (LPS). In continuation of earlier studies, structure determinations of liberated oligosaccharides and, where necessary, of intact LPS, were by H-1-NMR spectroscopy, Smith degradation, chromium trioxide and enzymic degradations, in conjunction With methylation studies supported by fast-atom-bombardment mass spectrometry and linkage analyses by gas chromatography/mass spectrometry. It was concluded on the basis of the following structures, in which each was linked 1-->5 to a terminal 3-deoxy-D-manno-octulosonic acid residue, that the core regions with qualititatively similar sugar compositions showed serotypic differences in one or more of their sequences, linkage types, and anometic configurations: [GRAPHICS] The outer regions of each structure carry Neu5Ac residues linked 2-->3 to available beta-D-Galp residues and show striking similarities with various glycosphingolipids of the ganglioside family. However, Neu5Ac epitopes are not apparently involved in determining serospecificity

Chemical structures of the core regions of campylobacter jejuni serotypes o:1, o:4, o:23, and o:36 lipopolysaccharides

Complete structures, including the location of N-acetylneuraminic acid (Neu5Ac) residues, were assigned for the core regions of Campylobacter jejuni serotypes 0:1, 0:4, and 0:23 and 0:36 lipopolysaccharides (LPS). In continuation of earlier studies, structure determinations of liberated oligosaccharides and, where necessary, of intact LPS, were by H-1-NMR spectroscopy, Smith degradation, chromium trioxide and enzymic degradations, in conjunction With methylation studies supported by fast-atom-bombardment mass spectrometry and linkage analyses by gas chromatography/mass spectrometry. It was concluded on the basis of the following structures, in which each was linked 1-->5 to a terminal 3-deoxy-D-manno-octulosonic acid residue, that the core regions with qualititatively similar sugar compositions showed serotypic differences in one or more of their sequences, linkage types, and anometic configurations: [GRAPHICS] The outer regions of each structure carry Neu5Ac residues linked 2-->3 to available beta-D-Galp residues and show striking similarities with various glycosphingolipids of the ganglioside family. However, Neu5Ac epitopes are not apparently involved in determining serospecificity

Chemical structure of the core region of campylobacter jejuni serotype o:2 lipopolysaccharide

The complete structure for the core region of Campylobacter jejuni serotype O:2 lipopolysaccharide (LPS) was assigned through studies on derivatives of the liberated oligosaccharide (OS 2) and the intact LPS. Structure determinations were performed using H-1-NMR spectroscopy, methylation studies supported by fast-atom-bombardment mass spectrometry and linkage analysis by gas chromatography/mass spectrometry, Smith degradation, and oxidation with chromium trioxide. It was concluded that complete oligosaccharide chains had the following structure: [GRAPHICS

Chemical structure of the core region of campylobacter jejuni serotype o:2 lipopolysaccharide

The complete structure for the core region of Campylobacter jejuni serotype O:2 lipopolysaccharide (LPS) was assigned through studies on derivatives of the liberated oligosaccharide (OS 2) and the intact LPS. Structure determinations were performed using H-1-NMR spectroscopy, methylation studies supported by fast-atom-bombardment mass spectrometry and linkage analysis by gas chromatography/mass spectrometry, Smith degradation, and oxidation with chromium trioxide. It was concluded that complete oligosaccharide chains had the following structure: [GRAPHICS

Chemical structure of the core region of campylobacter jejuni serotype o:2 lipopolysaccharide

The complete structure for the core region of Campylobacter jejuni serotype O:2 lipopolysaccharide (LPS) was assigned through studies on derivatives of the liberated oligosaccharide (OS 2) and the intact LPS. Structure determinations were performed using H-1-NMR spectroscopy, methylation studies supported by fast-atom-bombardment mass spectrometry and linkage analysis by gas chromatography/mass spectrometry, Smith degradation, and oxidation with chromium trioxide. It was concluded that complete oligosaccharide chains had the following structure: [GRAPHICS